Perfluoroelastomers are items of commerce, used for instance when a rubber with excellent heat and/or chemical resistance is needed. Thus they are used for seals of various types such as o-rings and gaskets, in tubing, and as tank linings.
However this type of elastomer often is difficult to process and/or has poor low temperature properties (becomes stiff or brittle at lower temperatures). One sought after improvement for these elastomers has been a material which acts as a plasticizer to improve processing properties and/or low temperature properties. Such materials have been difficult to find, since the "plasticizer" should preferably be stable at the high temperatures to which the perfluoroelastomer may be exposed to in use, and should also not bleed (become separated from) the perfluoroelastomer, particularly after the perfluoroelastomer is crosslinked.
R. C. Evers, et al., J. Polym. Sci., Polym. Chem. Ed., vol. 19, p. 427-442 (1981) and E. J. Soloski, et al., J. Fluorine Chem., vol. 11, p. 601-612 (1978) describe the synthesis of polyperfluoroethers with nitrile end groups. These materials are described as being useful as intermediates for the preparation of higher molecular weight polymers.
U.S. Pat. No. 4,413,094 describes blends of tetrafluoroethylene/perfluoro(methyl vinyl ether)/nitrile containing copolymers with higher molecular weight poly(hexafluoropropylene oxide) (polyHFPO). The polyHFPO contains nitrile groups which are introduced by random copolymerization of a nitrile containing monomer when the polyHFPO are made, and therefore the nitrile groups are randomly distributed along the polyHFPO chain. No mention is made of polyperfluoroethers with nitrile end groups.